1. Field of the Invention
The field of the invention is a system for controlling slip of a drive wheel of a vehicle, which includes a reference value setting means for setting a reference value for slippage of the drive wheel and a drive wheel torque reduction means for reducing the torque of the drive wheel when the slippage of the drive wheel exceeds the reference value.
2. Description of the Prior Art
In a drive wheel slip control system for vehicles of the type mentioned above, there has conventionally been proposed such an arrangement that the reference value for slippage of the drive wheel, which allows an appropriate slip rate to be obtained, is corrected on the basis of the opening degree of an accelerator and when such opening degree becomes large, the reference value for the slippage of the drive wheel is increased. .For example, see Japanese Patent Application Laid-open No. 23831/87.
The afore-mentioned drive wheel slip control system is effective when a vehicle is driven in a sporty fashion such as at the time of spin-turn. When the accelerator is put in full-open position, however, the reference value for slippage of the drive wheel may rise excessively and deteriorate the drive wheel slip controlling function which should inherently be exhibited by the system.
Furthermore, since the degree of throttle opening which might bring the drive wheel into an excessive slipping condition is changed dependent on the coefficient of friction of road surface, the speed reduction ratio between a prime mover and the drive wheel and the like, if it is arranged to change the slipping condition of the drive wheel at an absolute position of the throttle opening, it then becomes impossible to establish a relationship between the slippage of the drive wheel under control and the inherent throttle opening degree, thus making it difficult to provide a delicate variation in the wheel slipping condition which a driver desires.